SMEX02 AMSR-E Level 3 Daily Gridded Brightness Temperatures, Iowa

Summary

This data set contains Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) level 3 daily gridded brightness temperatures, spatially subsetted to the state of Iowa, USA. The study period covers 1 June 2002 through 31 August 2002. The level 3 data were derived from AMSR-E level 2A source data. Each daily file contains data from the 6.9, 10.7, 18.7, 36.5, and 89.0 GHz channels. Data are provided in 83 binary files, and are available via FTP from NSIDC. This work was done as part of the Soil Moisture Experiment 2002 (SMEX02).

These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.

Citing These Data

Njoku, E. G. 2004. SMEX02 AMSR-E Level 3 Daily Gridded Brightness Temperatures, Iowa. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview Table

Category Description
Data format

Brightness temperature data files: two-byte binary format, big-endian
Latitude and longitude files: ASCII text

Spatial coverage and resolution State of Iowa, USA
39° N to 45° N, -98° W to -89° W
Temporal coverage 1 June through 31 August 2002
Tools for accessing data Use an appropriate application to view binary data.
Grid type and size 25 km cylindrical EASE-Grid projection
File naming convention Brightness temperature data file names use the following convention:
  Iowa_AMSR_E_L3_DailyLand_X1_YYYYMMDD.bin
  where:
  X1 = version number of the level 3 data
  YYYY = four-digit year
  MM = two-digit month
  DD = two-digit day

Latitude and longitude files are named "Iowa_lat.txt" and "Iowa_lon.txt".
File size Binary files are 40 KB each. Latitude and longitude files are 14 KB. Total volume is 3.2 MB.
Parameter(s) Brightness temperatures (K)
Procedures for obtaining data Data are available via FTP.

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. Document Information

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Eni G. Njoku
Steven Chan

Jet Propulsion Laboratory
Pasadena, California

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

2. Detailed Data Description

Format

The latitude and longitude data are ASCII files. Each daily brightness temperature file contains 24 data arrays of dimension 24 x 35 (rows/latitudes x columns/longitudes). The data are stored as two-byte, big-endian integers in column major order, where following along the stored contiguous data increases rows before columns. Data arrays are from the 6.9, 10.7, 18.7, 36.5, and 89.0 GHz channels (V and H). The order and spatial resolution of the 24 data arrays are shown in the following table.

Channel Type Resolution
TB06.9V Ascending 56 km
TB06.9H Ascending 56 km
TB10.7V Ascending 56 km
TB10.7H Ascending 56 km
TB18.7V Ascending 56 km
TB18.7H Ascending 56 km
TB36.5V Ascending 56 km
TB36.5H Ascending 56 km
TB36.5V Ascending 12 km
TB36.5H Ascending 12 km
TB89.0V Ascending 12 km
TB89.0H Ascending 12 km
TB06.9V Descending 56 km
TB06.9H Descending 56 km
TB10.7V Descending 56 km
TB10.7H Descending 56 km
TB18.7V Descending 56 km
TB18.7H Descending 56 km
TB36.5V Descending 56 km
TB36.5H Descending 56 km
TB36.5V Descending 12 km
TB36.5H Descending 12 km
TB89.0V Descending 12 km
TB89.0H Descending 12 km

File Naming Convention

Brightness temperature data file names use the following convention:
  Iowa_AMSR_E_L3_DailyLand_X1_YYYYMMDD.bin
  where:
  X1 = version number of the level 3 data
  YYYY = four-digit year
  MM = two-digit month
  DD = two-digit day

Latitude and longitude files are named "Iowa_lat.txt" and "Iowa_lon.txt".

File Size

Binary files are 40 KB each. Longitude and latitude files are 14 KB.

Spatial Coverage

The study area covers the state of Iowa in the United States.

Southernmost Latitude: 39 ° N
Northernmost Latitude: 45° N
Westernmost Longitude: -98° W
Easternmost Longitude: -89° W

Spatial Resolution

Each daily brightness temperature file contains data arrays from the 6.9, 10.7, 18.7, 36.5, and 89.0 GHz channels (V and H). The resolution is either 56 km or 12 km. The 6.9, 10.7, and 18.7 (V and H) data are 56 km resolution; the 89.0 GHz (V and H) data are 12 km resolution. The 36.5 GHz (V and H) data are provided with both 56 km and 12 km resolution. (Refer to the channel table in the Format section of this document.)

The 56 km and 12 km resolutions correspond to the Resolution 1 and Resolution 4 definitions contained in the AMSR-E/Aqua L2A Global Swath Spatially-Resampled Brightness Temperatures (Tb) documentation.

Projection

The data are in 25 km cylindrical EASE-Grid projection. Please see Processing Steps for details.

Temporal Coverage

The study was conducted 1 June through 31 August 2002.

Parameter or Variable

Parameter Description

This data set contains AMSR-E level 3 daily gridded brightness temperatures.

Unit of Measurement

Brightness temperatures are given in tenths Kelvin.

Parameter Values

The brightness temperature data values are in units of tenths Kelvin, and are written as two-byte integers. The data arrays are written sequentially in flat binary format on a big-endian UNIX machine.

Sample Images

The following sample images illustrate the 36.5 GHz (V) data in 56 km and 12 km resolution. Click on a thumbnail below to view the full image.

56 km Sample 12 km Sample
Click to view 56 km sample image Click to view 12 km sample image

Error Sources

Missing data due to measurement anomalies are indicated by zeros. Grid points in gaps between successive swaths have the value 8888.

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Binary files are 40 KB each. Longitude and latitude files are 14 KB. Total volume is 3.2 MB.

Software

The following MATLAB code illustrates how the data arrays can be read:

  fid = fopen('Iowa_AMSR_E_L3_DailyLand_X1_20020601.bin','r','ieee-be');
  TB06vr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB06hr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB10vr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB10hr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB18vr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB18hr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB36vr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB36hr1a = fread(fid,[24 35],'integer*2') * 0.1;
  TB36vr4a = fread(fid,[24 35],'integer*2') * 0.1;
  TB36hr4a = fread(fid,[24 35],'integer*2') * 0.1;
  TB89vr4a = fread(fid,[24 35],'integer*2') * 0.1;
  TB89hr4a = fread(fid,[24 35],'integer*2') * 0.1;
  TB06vr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB06hr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB10vr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB10hr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB18vr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB18hr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB36vr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB36hr1d = fread(fid,[24 35],'integer*2') * 0.1;
  TB36vr4d = fread(fid,[24 35],'integer*2') * 0.1;
  TB36hr4d = fread(fid,[24 35],'integer*2') * 0.1;
  TB89vr4d = fread(fid,[24 35],'integer*2') * 0.1;
  TB89hr4d = fread(fid,[24 35],'integer*2') * 0.1;
  fclose(fid);

Related Data Collections

4. Data Acquisition and Processing

Processing Steps

The level 3 data are derived from level 2A source data. (See the AMSR-E/Aqua L2A Global Swath Spatially-Resampled Brightness Temperatures (Tb) documentation.) Level 3 gridded data were derived by resampling the level 2A swath data to the 25 km cylindrical EASE-Grid projection, using bin-averaging, and then compositing the daily swaths into separate ascending and descending grids. To associate a given array value with its location, refer to the latitude file "Iowa_lat.txt" and the longitude file "Iowa_lon.txt." For details regarding the EASE-Grid projection, please see All About EASE-Grid.

5. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

AMSR-E Advanced Microwave Scanning Radiometer - Earth Observing System
ASCII American Standard Code for Information Interchange
CLPX Cold Land Processes Experiment
DMSP Defense Meteorological Satellite Program
EASE-Grid Equal-Area Scalable Earth Grid
FTP File Transfer Protocol
NSIDC National Snow and Ice Data Center
SMEX Soil Moisture Experiment
SMMR Scanning Multichannel Microwave Radiometer
SSM/I Special Sensor Microwave/Imager
URL Uniform Resource Locator

Document Creation Date

March 2004

Document URL

http://nsidc.org/data/docs/daac/nsidc0196_smex_amsr_e_l3.gd.html